// Problem: 
// Contest: 
// URL: 
// Memory Limit: 
// Time Limit: 
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
signed main()
{
	int t=1;
//	cin>>t;
	while(t--)
	{
		int n,ans=0,tmp;
		cin>>n;
		vector<int> v(n+1),w(n+1);
		for(int i=1;i<=n;i++)cin>>v[i];
		for(int i=1;i<=n/2;i++)
		{
			w[i]=v[n-i+1]-v[i];
			if(w[i]*w[i-1]>0)
			{
				tmp=w[i]>0?min(w[i],w[i-1]):max(w[i],w[i-1]);
				w[i]-=tmp;
				w[i-1]-=tmp;
				ans+=abs(tmp);
			}
		}
		for(int i=1;i<=n/2;i++)
		{
			ans+=abs(w[i]);
		}
		cout<<ans;
	}
	return 0;
}
